IRWIN, Pa. (AP) — A fiery Mitt Romney on Tuesday accused President Barack Obama of believing the government is more vital to a thriving economy than the nation’s workers and dreamers, scrambling to get back on message by declaring of Obama, “I’m convinced he wants Americans to be ashamed of success.”

The new Romney approach came as Democrats pressed for the release of more of Romney’s tax returns and hounded the Republican candidate over discrepancies in when he left his private equity firm. The conservative magazine National Review urged Romney to release more of his tax records.

Obama has been trying to keep Romney focused on matters other than the sluggish economy, even releasing a single-shot TV ad Tuesday that suggests Romney gamed the system so well that he may not have paid any taxes at all for years.

As the campaign’s tenor grew combative, Romney seized on comments Obama uttered while campaigning in Virginia last week. The president, making a point about the supportive role government plays in building the nation, said in part: “Somebody helped to create this unbelievable American system that we have that allowed you to thrive. Somebody invested in roads and bridges. If you’ve got a business, you didn’t build that. Somebody else made that happen.”

Obama later added: “The point is, is that when we succeed, we succeed because of our individual initiative, but also because we do things together.”

The challenger pounced.

“To say that Steve Jobs didn’t build Apple, that Henry Ford didn’t build Ford Motors, that Papa John didn’t build Papa John Pizza ... To say something like that, it’s not just foolishness,” Romney said from a campaign rally outside Pittsburgh. “It’s insulting to every entrepreneur, every innovator in America.”

Romney added: “I tell you this. I’m convinced that he wants Americans to be ashamed of success.”

The Obama campaign said Romney had distorted Obama’s message by taking him out of context. Obama’s intended point — one he made again in Texas on Tuesday — was that government plays a role in helping people and businesses succeed by building roads, hiring teachers and firefighters, and looking out for the public good.

“There are some things we do better together,” Obama said in San Antonio at the start of a lucrative fundraising day in Texas. “We rise or fall as one nation. That’s what I believe. That’s what our history tells us. That’s what our future demands. That’s why I’m running for a second term as president of the United States.”

A consistent part of Obama’s “bottom-up” economic message is that individual initiative and hard work should be rewarded. But in a war of words, with both sides eager to jump on any gaffe or inelegant phrase, Romney saw a way to paint Obama as a big-government Democrat.

During the new line of attack, his campaign also questioned Obama’s patriotism. Former New Hampshire Gov. John H. Sununu, a Romney supporter, told reporters that businesses that grow from the ground up made the U.S. economy the envy of the world. “It is the American way, and I wish this president would learn how to be an American,” he said.

Asked to clarify that incendiary remark, Sununu later said: “The president has to learn the American formula for creating business.” Still later, he told CNN he had made a mistake. “I shouldn’t have used those words. And I apologize for using those words.”

Romney is trying shift attention away from his business record and his tax returns with a fresh assault as Obama, anxious about losing his fundraising edge, turned to Republican-tilted Texas to raise millions of dollars from gay, Latino and big-dollar donors.

During public events, Obama has remained focused on distinguishing himself from Romney’s policies and background, limiting his criticism of Romney’s private equity firm, Bain Capital, to claims it promoted the outsourcing of jobs to countries like China and India.

Yet behind the scenes, Obama’s campaign is trying to push a much more hard-nosed message.

The goal is to pressure Romney to release an expansive number of tax returns and suggesting that Romney has benefited from offshore accounts and investments in foreign tax havens and that he has not been forthcoming on the amount of time he spent at the helm of Bain.

The Obama camp aired an ad in the Pittsburgh media market taking issue with Romney’s decision to only release two years of his personal tax returns, a full record from 2010 and an estimate for 2011. Obama officials have no evidence supporting the suggestion that Romney may have paid zero taxes in some previous years.

“We won’t know, and it’s not possible for anyone to know, until he releases further years of tax returns,” said Obama campaign spokeswoman Jen Psaki.

In an online editorial, The National Review urged Romney to release additional tax returns even though it agreed with him that the Obama campaign wanted the returns for a “fishing expedition.”

“By drawing out the argument over the returns, Romney is playing into the president’s hands,” the editorial stated. “He should release them, respond to any attacks they bring, and move on.”

Romney stepped up his criticism of Obama in Pennsylvania, which has been a tough presidential battleground for the Republican Party. He accused Obama of engaging in cronyism, citing federal grants and loan guarantees to alternative energy companies run by Obama backers and donors.

In choosing Texas to raise money, Obama ventured to a state that has not voted Democratic in a presidential contest since 1976. But Texas ranks among the states with the largest concentrations of wealth, along with New York, California, Florida and Illinois.

Republicans typically raise more in Texas than Democrats. So far this election, Obama has raised $4.5 million from the state and the Democratic National Committee has raised $1.7 million, compared with $7.1 million for Romney and $5.3 million for the Republican Party.

Obama held one event in San Antonio aimed in part at Latinos, featuring actress Eva Longoria. Another event in Austin is co-sponsored by the Democratic National Committee’s LGBT Council. He also scheduled two smaller events with high-dollar donors.